Weird sound in the cooling system when I turn off the engine on 2007 Mercedes-Benz GL450

I bought the car a few weeks ago and didn't notice it until a couple of days ago. When I turn off the engine, after a few seconds I hear a "ffffffff" sound. like if it was releasing some kind of pressure. Any one has any idea of what it could be??? Thanks.

by in Beverly Hills, CA on February 14, 2012
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1 answer 1 comment
ANSWER by , April 30, 2012
This sounds like it is the airmatic sytem that is releasing air from the air suspension. It's normal.
COMMENT by , May 02, 2012
Thanks so much for your answer. What a relief :)